Environmental Engineering Reference
In-Depth Information
8.13.6.2 Flow
The flow of return activated sludge is tested daily. Test results are
required to determine the mass balance and for control of the sludge
blanket, MLSS, and MLVSS. For waste activated sludge, flow is sampled
and tested whenever sludge is wasted. Results are required to determine
mass balance and to control solids level in process.
8.13.7 Process Control adjustments
In the routine performance of their duties, wastewater operators
make process control adjustments to various unit processes, including
the activated sludge process. Following is a summary of the process
controls available for the activated sludge process.
8.13.7.1 Process Control: Return Rate
Condition:
Return rate is too high.
result:
•
Hydraulic overloading of
aeration and settling tanks
•
Reduced aeration time
•
Reduced settling time
•
Loss of solids over time
Condition:
Return rate is too low.
result:
•
Septic return
•
Solids buildup in settling tank
•
Reduced MLSS in aeration tank
•
Loss of solids over weir
8.13.7.2 Process Control: Waste Rate
Condition:
Waste rate is too high.
result:
•
Reduced MLSS
•
Decreased sludge density
•
Increased
SVI
•
Decreased
MCRT
•
Increased F
/M ratio
